Fix passing of locals as function arguments with side-effects

Commit 75c22465cf8fe262edfe6178bb9ca19661fb710e regressed in allowing
locals and arguments to be passed directly as further arguments to function
calls, but that's incorrect when considering

    var i = 2;
    testFunction(i, i += 2)

where it is instrumental to place the first argument into a temp (making a
copy) instead of passing it directly.

Change-Id: Iffcf6c6eda92a8fb665982cda1db0b96359cd092
Task-number: QTBUG-45879
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

2 files changed, 22 insertions, 1 deletions

diff --git a/src/qml/compiler/qv4codegen.cpp b/src/qml/compiler/qv4codegen.cpp
index a7b5326861..260db0f0dd 100644
--- a/src/qml/compiler/qv4codegen.cpp
+++ b/src/qml/compiler/qv4codegen.cpp
@@ -538,7 +538,7 @@ IR::Expr *Codegen::subscript(IR::Expr *base, IR::Expr *index)
 
 IR::Expr *Codegen::argument(IR::Expr *expr)
 {
-    if (expr && !expr->asTemp() && !expr->asArgLocal()) {
+    if (expr && !expr->asTemp()) {
         const unsigned t = _block->newTemp();
         move(_block->TEMP(t), expr);
         expr = _block->TEMP(t);
diff --git a/tests/auto/qml/qjsengine/tst_qjsengine.cpp b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
index 2b7b1fc524..2690b857fa 100644
--- a/tests/auto/qml/qjsengine/tst_qjsengine.cpp
+++ b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
@@ -176,6 +176,8 @@ private slots:
     void intConversion_QTBUG43309();
     void toFixed();
 
+    void argumentEvaluationOrder();
+
 signals:
     void testSignal();
 };
@@ -3628,6 +3630,25 @@ void tst_QJSEngine::toFixed()
     QCOMPARE(result.toString(), QStringLiteral("12.1"));
 }
 
+void tst_QJSEngine::argumentEvaluationOrder()
+{
+    QJSEngine engine;
+    QJSValue ok = engine.evaluate(
+            "function record(arg1, arg2) {\n"
+            "    parameters = [arg1, arg2]\n"
+            "}\n"
+            "function test() {\n"
+            "    var i = 2;\n"
+            "    record(i, i += 2);\n"
+            "}\n"
+            "test()\n"
+            "parameters[0] == 2 && parameters[1] == 4");
+    qDebug() << ok.toString();
+    QVERIFY(ok.isBool());
+    QVERIFY(ok.toBool());
+
+}
+
 QTEST_MAIN(tst_QJSEngine)
 
 #include "tst_qjsengine.moc"